He has called for a holy war against America.
He dislikes America because he thinks they helped the people he insists on describing as enemies of his religion - the Israeli Jews - during wars in the Middle East.
Osama Bin Laden is a very rich man.
He is the leader of a group called al-Qaeda. He has thousands of followers.
He is thought to be behind other attacks including a bombing at the World Trade Center in 1993 and car bombings outside the US Embassies in Kenya and in Tanzania.